Electrospun scaffolds for multiple tissues regeneration in vivo through topography dependent induction of lineage specific differentiation.

Physical topographic cues from various substrata have been shown to exert profound effects on the growth and differentiation of stem cells due to their niche-mimicking features. However, the biological function of different topographic materials utilized as bio-scaffolds in vivo have not been rigorously characterized. This study investigated the divergent differentiation pathways of mesenchymal stem cells (MSCs) and neo-tissue formation trigged by aligned and randomly-oriented fibrous scaffolds, both in vitro and in vivo. The aligned group was observed to form more mature tendon-like tissue in the Achilles tendon injury model, as evidenced by histological scoring and collagen I immunohistochemical staining data. In contrast, the randomly-oriented group exhibited much chondrogenesis and subsequent bone tissue formation through ossification. Additionally, X-ray imaging and osteocalcin immunohistochemical staining also demonstrated that osteogenesis in vivo is driven by randomly oriented topography. Furthermore, MSCs on the aligned substrate exhibited tenocyte-like morphology and enhanced tenogenic differentiation compared to cells grown on randomly-oriented scaffold. qRT-PCR analysis of osteogenic marker genes and alkaline phosphatase (ALP) staining demonstrated that MSCs cultured on randomly-oriented fiber scaffolds displayed enhanced osteogenic differentiation compared with cells cultured on aligned fiber scaffolds. Finally, it was demonstrated that cytoskeletal tension release abrogated the divergent differentiation pathways on different substrate topography. Collectively, these findings illustrate the relationship between topographic cues of the scaffold and their inductive role in tissue regeneration; thus providing an insight into future development of smart functionalized bio-scaffold design and its application in tissue engineering.

The regulation of tendon stem cell differentiation by the alignment of nanofibers.

Tendon is a specific connective tissue composed of parallel collagen fibers. The effect of this tissue-specific matrix orientation on stem cell differentiation has not been investigated. This study aimed to determine the effects of nanotopography on the differentiation of human tendon stem/progenitor cells (hTSPCs) and develop a biomimetic scaffold for tendon tissue engineering. The immuno-phenotype of fetal hTSPCs was identified by flow cytometry. The multipotency of hTSPCs toward osteogenesis, adipogenesis, and chondrogenesis was confirmed. Then, the hTSPCs were seeded onto aligned or randomly-oriented poly (l-lactic acid) nanofibers. Scanning electron micrographs showed that hTSPCs were spindle-shaped and well orientated on the aligned nanofibers. The expression of tendon-specific genes was significantly higher in hTSPCs growing on aligned nanofibers than those on randomly-oriented nanofibers in both normal and osteogenic media. In addition, alkaline phosphatase activity and alizarin red staining showed that the randomly-oriented fibrous scaffold induced osteogenesis, while the aligned scaffold hindered the process. Moreover, aligned cells expressed significantly higher levels of integrin alpha1, alpha5 and beta1 subunits, and myosin II B. In in vivo experiments, the aligned nanofibers induced the formation of spindle-shaped cells and tendon-like tissue. In conclusion, the aligned electrospun nanofiber structure provides an instructive microenvironment for hTSPC differentiation and may lead to the development of desirable engineered tendons.